{“success”:false,“error”:{“code”:“ACCESS_DENIED”,“message”:“Permission to perform the operation is denied for id”}}

if($challengeResult['success']) {
        $accessKey = md5($challengeResult['result']['token']."FsMuMfcT4Iwp0ne");
        $postArray = array('operation' => 'login', 'username' => 'admin', 'accessKey' => $accessKey);
        print_r($postArray);
        $loginResult = json_decode(sendPostRequest($site_URL."/webservice.php", $postArray), true);

the login is successfully but when i add some data.

$data = array(
                 'subject'=>'AutoGen PurchaseOrder',
                 'assigned_user_id' => vtws_getWebserviceEntityId('Users',1),
                 'postatus'=>'Created',
                 'bill_street'=>'325, 1st Floor, Sant Nagar',
                 'bill_city' => 'New Delhi',
                 'bill_state' => 'Delhi',
                 'bill_code' => '110065',
                'bill_country' => 'India',
                 'ship_street'=>'325, 1st Floor, Sant Nagar',
                 'ship_city' => 'New Delhi',
                 'ship_state' => 'Delhi',
                 'ship_code' => '110065',
                 'ship_country' => 'India',
                 'cf_898'  => '200140',
                 'vendor_id' => vtws_getWebserviceEntityId('Vendors',$_POST['fromwarehouse_id']), //
 Products from
                 'cf_1054' => 'Normal', // PurchaseOrder type
                 'productid' => vtws_getWebserviceEntityId('Products',2),
                 'LineItems'=>$lineItems
             );

the result i get is

"code":"ACCESS_DENIED","message":"Permission to perform the operation is denied for id"